1. Field of the Invention
The invention relates to materials which are crosslinkable at room temperature by condensation and are based on organosilicon compounds which cure to give permanently resilient materials.
2. Background Art
One-component sealing compounds which are storable in the absence of water and crosslink on admission of water with elimination of, for example, alcohols at room temperature to give elastomers, also referred to as RTV-1 sealing compounds, are known. These products are used, for example, in large amounts in the construction industry.
The basis of these RTV-1 sealing compounds are polymers with silyl groups which have reactive substituents such as OH groups or hydrolyzable alkoxy groups. Furthermore, these sealing compounds may have various fillers, plasticizers, adhesion promoters, catalysts and so-called crosslinking agents or further additives, such as, for example, colored pigments, rheology additives or fungicides.
The prior art has already disclosed various RTV-1 compounds. WO 01/49774 A2 and EP 1 254 192 B1 describe, for example, materials containing various titanium esters, mixed esters and titanium chelates. However, these have the known disadvantages of Ti, such as, for example, yellowing, surface tack, slow vulcanization rate and stability problems during storage. A further disadvantage is the incompatibility of many titanium compounds with customary aminosilane-based adhesion promoters.
There are various approaches for solving these problems. Regarding the yellowing problem, U.S. Pat. No. 4,906,719 discloses, for example, the addition of organomercaptans as additives. EP 0 747 443 A2 and DE 42 13 873 A1 describe titanium complexes with oxygen donors which show reduced yellowing.
In order to solve the problem of surface tack or slow vulcanization, EP 0 853 101 A1 describes a mixture which contains alkoxysilanes and which must comply with a certain molar ratio between the individual starting materials.
In order to solve the problem of low storage stability, DE 44 27 528 A1 describes the use of cyclically substituted complexes based on diolates of the metals of the 4th subgroup in silicone compositions.
In order to avoid the incompatibility of many titanium compounds with customary aminosilane-based adhesion promoters, methods were developed, as described in DE 22 28 645 A1 and EP 1 209 201 A1, which also avoid crepe hardening on compounding. However, this has the disadvantage that a more complicated two-stage compounding sequence is necessary.
The prior art, for example, DE 103 19 303 A1 and DE 10 2006 060 357 A1, discloses RTV-1 materials which furthermore contain dibutyl- or dioctyltin compounds as catalysts since these do not have disadvantages such as yellowing, low storage stability and in particular aminosilane incompatibility. The use of organotin compounds is, however, now controversial since limitations were imposed on the use of dibutyl- and dioctyltin compounds by amendment of EU Directive 76/769/EEC of May 28, 2009.
EP 1 230 298 A1 describes the use of salts of tin, zinc, iron, barium, zirconium and lead, preferably as metal salt carboxylates, and metal octanoates of iron and lead as a tin-free system. However, the disadvantage that these compounds are slow catalysts is common to all of them. Moreover, some of the compounds described there are unsafe for health reasons. In addition to the previous statements regarding tin compounds, for example, Ba carboxylates, as hazardous substances of class R20/22 according to the German regulation on hazardous material, are subject to mandatory labeling.